But I think if you offer a game for free to users with the understanding that their computer will be used to mine bitcoins continuously (but never exceeding, say, 5% CPU), a lot of users will still take you up on the offer. The power of free! I'm not sure if even that revenue will be meaningful, though.
Not giving payment info /is/ a huge advantage, especially for small payments. I mean, even when everyone pays for their own power, I think for payments up to a few dollars a month, people would pay twice as much to not have to deal with giving payment info. (this is different from, but similar to the old payment process of having your computer dial a toll-number to get access, because you have a lot more control over and understanding of how much power your system is drawing. It also won't show up on your phone bill.)
Then, think of the large number of gamers who don't have credit cards, and how many of those folks who don't have credit cards /also/ don't pay for their own electricity.
This sounds like the perfect way for a company that doesn't care about ethics to get children to pay for things.
They should be happy to be buried up to their eyeballs in debt with useless degrees and a job at starbucks.